Merychippus

Merychippus is an extinct proto-horse of the family Equidae that was endemic to North America during the Miocene, 15.97–5.33 million years ago. It had three toes on each foot and is the first horse known to have grazed.

==Discovery and naming== thumb|left|Restoration of Merychippus insignis Merychippus was named by Joseph Leidy (1856). Numerous authors assigned the type species – Merychippus insignis – to Protohippus, but this is ignored. It was assigned to the Equidae by Leidy (1856) and Carroll (1988), and to the Equinae by MacFadden (1998) and Bravo-Cuevas and Ferrusquía-Villafranca (2006). The genus name comes from Ancient Greek μηρυκασθαι (mērukasthai), meaning "to ruminate", and ἵππος (híppos), meaning "horse", but current evidence does not support Merychippus ruminating.